The present invention relates to a device for the removal of waste products or residues created during the thermal separation of material, when a device such as a plasma torch is used, by means of a foam.
Elimination of waste products during the thermal separation of material is presently carried out by several methods. The waste products are removed either by suction or by use of a water working table. When a water working table is used, water is kept in a reservoir which reaches either below or over the level of the material to be separated. When a plasma torch is used to cut the material, it is also provided with an annular jet of water around the torch, which forms a protective mantle.
The disadvantages of the removal of waste products by suction are that a suction device causes a substantial increase in the decibel level in its vicinity, which is deleterious to the operator of the device. In addition, substantial losses of heat occur near the torch, due to the removal of the surrounding atmosphere by the suction device.
Furthermore, when a suction device is used with a plasma torch, a special filtering unit is often needed to remove certain gases, such as nitrous gases, from the atmosphere removed by the suction device as their level has increased. Thus, the cost for a suction unit, with the special filtering unit, can often exceed the cost of the plasma torch.
The drawback of using water working tables for the removal of waste products occurs when the water does not reach over the material to be cut. If the torch is not kept under the water level or the annular jet of water, forming a mantle around the torch, is not used, harmful waste products pass around the torch to the atmosphere. However, when the torch is kept under the water level or if the annular jet of water is used, it is difficult to control the torch height above the material to be cut and difficult to control the thermal process, thus decreasing the cutting efficiency. Another drawback is that the water, when it removes the residues, contains substantial amounts of impurities and thus cannot be disposed of by discharge into the sewage system.
Another known method of removing residues, when a plasma torch is used, involves surrounding the plasma flow with a layer made of either a powdered material or a foam or a liquid. Spraying of this layer takes place during the burning process, in the area around the cutting zone and below the material to be cut. The drawback of this process, when a powdered material is used, is that harmful gases, such as phosgenes and hydrogen fluorides, are formed, during the decomposition of the powdered material. When only foam or liquid is used, while removal of the residues is solved, the problem connected with water working tables arises, namely disposal of the saturated material.